JavaScript regular expression validation for domain name?

Question

How to check a valid domain name and username with regular expression in JavaScript?

function validate()
{
    var         


        

Answer 1

This code support sub-domains too:

^(([a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9]|[a-zA-Z0-9])\.)*[a-zA-Z0-9][a-zA-Z0-9-]{1,61}[a-zA-Z0-9]\.[a-zA-Z]{2,}$